The present invention relates to a drawing apparatus which draws a pattern on a substrate with a plurality of charged-particle beams, a control method thereof, and a device manufacturing method.
An example of a multi-charged-particle beam exposure apparatus using a plurality of charged-particle beams is an electron beam exposure apparatus proposed in the 62nd Annual Meeting of the Japan Society of Applied Physics (lecture: No. 11a-C-5). FIGS. 11A and 11B are schematic views showing this electron beam exposure apparatus. In FIGS. 11A and 11B, a plurality of electron beams from a plurality of electron sources ES which emit electrons irradiate a wafer W serving as a surface to be exposed via magnetic lenses ML of a magnetic lens array MLA. The magnetic lens array MLA is constituted by vertically arranging, at an interval, magnetic disks MD having a plurality of openings of the same shape. The magnetic disks MD are excited by a common coil CC. Each opening functions as the magnetic pole of each magnetic lens ML, and generates the same lens magnetic field in design.
The exposure apparatus has the following features. (1) A plurality of electron beams enter the wafer W without crossing each other, the Coulomb effect between a plurality of electron beams can be ignored, and the wafer can be irradiated with an electron beam of a large current. (2) The coil as an excitation means is shared by a plurality of magnetic poles, and arranged outside the plurality of magnetic poles. This allows arraying a plurality of magnetic lenses close to each other, and arranging a plurality of electron beams at a high density.
With these two features, a higher throughput of the exposure apparatus is expected.
Owing to nonuniformity in the permeability and opening shape of the magnetic disk, electron-optic characteristics change between a plurality of magnetic lenses which constitute the magnetic lens array. To correct this difference, each magnetic lens array must be equipped with an electron-optic element serving as an adjuster which adjusts electron-optic characteristics. However, a plurality of magnetic lenses are arranged close to each other, and the adjustment amount is restricted due to downsizing of the adjustment electron-optic element and reduction in the interference between electron-optic elements. It is difficult to adjust all the optical characteristics of a plurality of magnetic lenses to a target value.
The present invention has been made in consideration of the above situation, and has as its object to accurately correct, e.g., the electron-optic characteristics of a plurality of magnetic lenses which constitute a magnetic lens array.
According to the first aspect of the present invention, there is provided an exposure apparatus which draws a pattern on a substrate with a plurality of charged-particle beams, comprising a charged-particle beam generation source which generates a plurality of charged-particle beams grouped into a plurality of groups each formed from at least one charged-particle beam, a magnetic lens array which is constituted by arraying a plurality of magnetic lenses corresponding to the plurality of groups between the charged-particle beam generation source and a substrate stage which supports the substrate, the plurality of magnetic lenses being excited by a common excitation unit, a plurality of electron-optic elements which are arranged in correspondence with the plurality of groups and individually correct electron-optic characteristics of the plurality of magnetic lenses, and a control system which controls the common excitation unit to adjust the electron-optic characteristics of the plurality of magnetic lenses at once, and individually controls the plurality of electron-optic elements to individually correct the electron-optic characteristics of the plurality of magnetic lenses, thereby optimizing an image formed on the substrate with the plurality of charged-particle beams grouped into the plurality of groups.
According to a preferred aspect of the present invention, the control system preferably controls the common excitation unit so as to minimize a maximum value of differences between the electron-optic characteristics of the plurality of magnetic lenses and a target characteristic.
According to another preferred aspect of the present invention, the control system preferably controls the common excitation unit and the plurality of electron-optic elements so as to make a focal position of each of the plurality of magnetic lenses coincide with a target position.
According to still another preferred aspect of the present invention, each group may be formed from a plural charged-particle beams. The control system preferably controls the common excitation unit and the plurality of electron-optic elements every group so as to correct at least one of magnification and rotation of images each of which is formed on the substrate with the plural charged-particle beams of one group. This is realized when, for example, each electron-optic element has a plurality of deflectors which deflect a plurality of charged-particle beams passing through the electron-optic element, and the control system individually controls the plurality of deflectors arranged for the electron-optic element. Alternatively, each electron-optic element may have a plurality of incident position changing elements which change incident positions of a plurality of charged-particle beams passing through the electron-optic element on corresponding magnetic lenses, and the control system may individually control the plurality of incident position changing elements arranged for the electron-optic element, thereby correcting at least one of magnification and rotation of the image formed on the substrate.
The second aspect of the present invention relates to a method of controlling an exposure apparatus which draws a pattern on a substrate with a plurality of charged-particle beams. The exposure apparatus includes a charged-particle beam generation source which generates a plurality of charged-particle beams grouped into a plurality of groups each formed from at least one charged-particle beam, a magnetic lens array which is constituted by arraying a plurality of magnetic lenses corresponding to the plurality of groups between the charged-particle beam generation source and a substrate stage which supports the substrate, the plurality of magnetic lenses being excited by a common excitation unit, and a plurality of electron-optic elements which are arranged in correspondence with the plurality of groups and individually correct electron-optic characteristics of the plurality of magnetic lenses. The control method comprises the first step of adjusting the electron-optic characteristics of the plurality of magnetic lenses at once by controlling the common excitation unit, and the second step of individually correcting the electron-optic characteristics of the plurality of magnetic lenses by individually controlling the plurality of electron-optic elements. An image formed on the substrate with the plurality of charged-particle beams grouped into the plurality of groups is optimized by the first and second steps.
According to the third aspect of the present invention, there is provided a manufacturing method of manufacturing a device through a lithography step, wherein the lithography step includes the step of drawing a pattern on a substrate using the above exposure apparatus.
According to the fourth aspect of the present invention, there is provided a manufacturing method of manufacturing a device through a lithography step, wherein the lithography step includes the step of drawing a pattern on a substrate using an exposure apparatus controlled by the above control method.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.